Stock Options And Employee Stock Purchase Plan (Restricted Stock) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Compensation cost recognized	$ 2,425,000	$ 2,403,000	$ 7,108,000	$ 6,851,000
Allocated Share-based Compensation Expense	2,425,000	2,403,000	7,108,000	6,851,000
Restricted Stock And Restricted Stock Unit (RSU) [Member]
Compensation cost recognized	1,800,000	1,600,000	5,000,000	3,700,000
Allocated Share-based Compensation Expense	1,800,000	1,600,000	5,000,000	3,700,000
Unrecognized compensation cost related to non-vested awards granted	18,500,000		18,500,000		16,000,000
Restricted Stock [Member]
Shares, Nonvested at January 1, 2013			828,475
Shares, Granted			178,430
Shares, Vested			(291,841)
Shares, Canceled			(43,900)
Shares, Nonvested at September 30, 2013	671,164		671,164
Weighted-Average Grant-Date Fair Value, Nonvested at January 1, 2013			$ 23.08
Weighted-Average Grant-Date Fair Value, Granted			$ 38.40
Weighted-Average Grant-Date Fair Value, Vested			$ 21.33
Weighted-Average Grant-Date Fair Value, Canceled			$ 24.46
Weighted-Average Grant-Date Fair Value, Nonvested at September 30, 2013	$ 27.82		$ 27.82
Weighted-average period to recognize compensation cost (in years)			2 years 7 months 21 days
Restricted Stock Units (RSUs) [Member]
Shares, Nonvested at January 1, 2013			115,466
Shares, Granted			26,675
Shares, Vested			(10,116)
Shares, Canceled			(33,000)
Shares, Nonvested at September 30, 2013	99,025		99,025
Share Based Compensation Equity Awards Other Than Options Expected To Vest Shares			67,640
Weighted-average period to recognize compensation cost (in years)			3 years 8 months 19 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms			2 years 3 months 11 days
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Expected To Vest Weighted Average Remaining Contractual Term			2 years 0 months 4 days
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Expected To Vest Intrinsic Value	3,349,522		3,349,522
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding, Aggregate Intrinsic Value	$ 4,903,718		$ 4,903,718